Process for the reoxidation of photographic bleaching and bleach-fix baths

ABSTRACT

PHOTOGRAPHIC BLEACHING AND BLEACH-FIXING BATHS ARE REOXIDIZED BY SPRAYING THEM THROUGH A NOZZLE IN THE PRESENCE OF OXYGEN INTO AN OXIDATION CHAMBER. THE OXYGEN IS PROVIDED EITHER IN THE FORM OF AIR OR PURE OXYGEN, WHICH MAY BE INTERMIXED AT THE NOZZLE OR CONTACTED IN THE CHAMBER ATMOSPHERE. THE GASES AND LIQUID CONSTITUENTS OF THE SPRAYED BATHS ARE SEPARATED BY DIRECTING THEM THROUGH BAFFLED PASSAGEWAYS OR BUBBLING THROUGH A LIQUID. THE BAFFLED PASSAGEWAYS MAY BE DISPOSED CONCENTRICALLY ABOUT THE OXIDATION CHAMBER OR IN ITS BOTTOM. THE NOZZLES FOR LIQUID AND GAS ATOMIZATION MAY BE DIRECTED IN THE SAME OR OPPOSITE DIRECTIONS OR IN SEPARATE OR COMBINED NOZZLES. A LIQUID FOR BUBBLING SEPARATION MAY BE CONCENTRICALLY DISPOSED IN A JACKET ABOUT THE BOTTOM OF THE OXIDATION CHAMBER INTO WHICH THE LIQUID AND GASEOUS CONSTITUENTS ARE FORCED BY EXCESS PRESSURE. THE LIQUID IS DISCHARGED FROM AN OVERFLOW NEAR THE TOP OF THE JACKET AND THE GASEOUS CONSTITUENTS ARE SEPARATED BY BUBBLING THROUGH THE JACKET. REOXIDATION MAY BE PERFORMED DIRECTLY WITHIN THE BLEACH OR BLEACH-FIXING CHAMBER AND MAY BE PERFORMED AT THE SAME TIME AS THE BATHS ARE SPRAYED UPON THE SILVER HALIDE EMULSION LAYERS OF AN EXPOSED PHOTOGRAPHIC MATERIAL. SILVER SALTS ARE REMOVED FROM THE BATHS BEFORE THEY ARE SPRAYED, AND THE PHOTOGRAPHIC MATERIAL MAY FORM PART OF THE WALL OF THE CHAMBER.   D R A W I N G

May 28, 1974 KARL'WILHELM SCHRANZ E A 3, ,246 PROCESS FOR THEREOXIDATIONOF PHQTQGRAPHIC -FIX BATHS BLEACHING AND BLEACH Filed March17. 1972 4 Sheets-Sheet 1 A r/v I z H I I I Filed March 17. 1972 May 28,1974 KARL-WILHELM SCHRANZ EI'AL PROCESS FOR THE REOXIDATION OFPHOTOGRAPHIC BLEACHING AND BLEACH-FIX BATHS 40a r -I M i Fig. A

4 Sheets-Sheet 2 y 1974 KARL--WILHELM SCHRANZ ETAL 3,813,246 PROCESS FORTHE REOXIDATION OF PHOTOGRAPHIC BLEACHING AND BLEACH-FIX BATHS FiledMarch 17. 1972 4 sh'eets-sh t 4 Fig. 6'

United States Patent 3,813,246 PROCESS FOR THE REOXIDATION 0F PHOTO- US.CI. 96-60 BF Claims ABSTRACT OF THE DISCLOSURE Photographic bleachingand bleach-fixing baths are reoxidized by spraying them through a nozzlein the presence of oxygen into an oxidation chamber. The oxygen isprovided either in the form of air or pure oxygen, which maybeintermixed at the nozzle or contacted in the chamber atmosphere. Thegases and liquid constituents of the sprayed baths are separated bydirecting them through baffied passageways or bubbling through a liquid.The baflied passageways may be disposed concentrically about theoxidation chamber or in its bottom. The nozzles for liquid and gasatomization may be directed in the same or opposite directions or inseparate or combined nozzles. A liquid for bubbling separation may beconcentrically disposed in a jacket about the bottom of the oxidationchamber into which the liquid and gaseous constituents are forced byexcess pressure. The liquid is discharged from an overflow near the topof the jacket and the gaseous constituents are separated by bubblingthrough the jacket. Reoxidation may be performed directly within thebleach or bleach-fixing chamber and may be performed at the same time asthe baths are sprayed upon the silver halide emulsion layers of anexposed photographic material. Silver salts are removed from the bathsbefore they are sprayed, and the photographic material may form part ofthe wall of the chamber.

BACKGROUND OF THE INVENTION The invention relates to a process for thereoxidation of photographic bleaching and bleach fix baths, in whichprocess the said baths are sprayed in the presence of oxygen.

It is known to spray-photographic baths on to photographic materialswhich are to be processed by means of spray nozzle systems. The mainadvantage of this process is that the bath is applied uniformly and onlyto that side of the material which carries the photographic layer withvigorous agitation so that the time required for the individualprocessing steps is very short. It is also known that when aphotographic developer bath is applied by spraying in the presence ofoxygen the bath is very liable to undergo oxidative changes which mayimpair the results of the process. It is therefore generally necessaryto add antioxidants to a bath which is to be sprayed in order tocounteract this effect or to apply the spray with the substantialexclusion of oxygen.

It has not previously been known that the oxidative change whichinevitably occurs when spraying photographic baths can be utilized forthe photographic process.

When processing color photographic material based on silver halide, thephotographic material must be treated ice either with a bleaching bathand a fixing bath or with a bleach fix bath after the color developmentin order to remove the image silver and any silver halide still presentafter development. This treatment converts the silver image into asilver salt by the oxidizing properties of the bleaching agent, and thesilver salt is converted into a readily watersoluble form by the fixingagent. In order that the bleaching agent may be used again for thephotographic process it must be reoxidized. When bleach-fix baths areused, reoxidation is preceded by electrolytic or chemical desilvering ofthe bath. Reoxidation of the bleach-fix bath combined with desilveringis gaining a position of increasing importance due to increasinglystringent legal requirements to prevent pollution of efiiuent water andto the increasing cost of silver. The oxidation process may be initiatedin known manner by chemical compounds such as bromine, potassiumpersulfate or potassium bromate or by blowing air into the bleachingbath or bleach-fix bath. Most chemical oxidizing agents, however, leadto an accumulation of salts in the baths which may cause the bleachingprocess to be considerably impaired.

The method of injecting air into the bleaching bath or bleach-fix bath,on the other hand, requires the use of large storage tanks because therate of oxidation is low due to the comparatively small phase interfacebetween the gaseous atmospheric oxygen and the bleaching bath andconsequently a long time is required for reconstituting the bleachingbath or bleach-fix bath.

It is an object of this invention to provide a simple and economicalprocess for the reoxidation of used photographic bleaching andbleach-fix baths whereby the baths are rapidly made available again foruse without being impaired by the accumulation of foreign salts.

SUMMARY OF THE INVENTION It has now been found that used bleaching andbleachfix baths can be reoxidized by spraying in the presence of oxygen.

This invention therefore relates to a process for the reoxidation ofphotographic bleaching and bleach-fix baths which is characterized inthat the photograpic baths are sprayed in the presence of oxygen in anoxidation chamber and that the spray mist is subsequently separated intogaseous and liquid constituents in a separator. The invention alsorelates to various apparatus for carrying out this process.

The baths which are to be reoxidized are finely sprayed or atomized bymeans of spray nozzle systems in an oxidation chamber, the oxygenrequired for reoxidation being supplied in the form of pure oxygen orair. The apparatus according to the invention are provided withseparators which enable the spray mist formed in the oxidation chamberto be separated into gaseous constituents (effluent air) and liquidconstituents (bleaching or bleach-fix baths) and which ensure that theelfiuent air is not 'discharged until it is free from spray. Theeffluent, from which oxygen has been partly or completely removed, maythen be either introduced into another reaction chamber, e.g. to serveas protective gas for photographic processes which are sensitive tooxidation, or reused for the reoxidation process in the spray chamber,but the oxygen used up in the process of reoxidation is advantageouslyreplaced bv the addition of fresh air or oxygen.

BRIEF DESCRIPTION OF THE DRAWING Further details and advantages of theinvention will be clear from the claims in conjunction with thedescription of practical examples which are explained in detail withreference to the figures of the drawing in which:

FIG. 1 shows an apparatus for the reoxidation of bleaching andbleach-fix baths by the process according to 3 t the invention, in whichthe separator surrounds the oxidation chamber;

FIG. 2 shows another apparatus for the process according to theinvention, in which the separator is situated immediately below. theoxidation chamber; and FIG. 3 shows another apparatus for the processaccording to the-invention, in which ventilation of the oxidationchamber is effected by way of a bubbling vessel.

; FIG. 4 shows schematically the recirculating air process in which theair leaving the oxidation chamber is partly used again for spraying thebath, and the oxygen used up in the oxidation reaction is supplied byadmixture of oxygen or fresh air.

, FIG. 5 shows an apparatus for carrying out simultaneously thereoxidation of bleaching or bleach-fix baths and the bleaching orbleach-fixing, both by spraying the bath in thepresence of oxygen inthesame chamber.

1 FIG. 6 shows an apparatus according to the invention consisting of. anoxidation chamber and a bubbling vessel which functions as a separatorand constitutes the processing tank for the bleaching or bleach-fixingprocess.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 1' FIG. 1 shows a longitudinalsection through an apparatus for the reoxidation of bleaching andbleach-fix baths. The oxidation chamber 105 is formed by an uprightcylindrical tube 110 (wall of oxidation chamber) which is open at thetop and rigidly connected to a horizontal base plate 109 at the bottomthrough which the two component nozzle 102 extends axially and opensinto the oxidation chamber. The oxidation chamber 105 is surroundedcoaxially by a wider tube 112 (wall of housing) which is closed at thetop by the cover plate 111 and is also rigidly connected with thebaseplate 109 and which together with the cover plate 111 forms thehousing of the separator 106. The atomized spray composed of bleachingor bleach-fix bath supplied through feed tube 103 and air suppliedthrough feed tube 104 is discharged at the top of the two-componentnozzle 102 to enter the oxidation chamber 105 where reoxidation of thebleaching agent substantially takes place. Most of the atomizedbleaching or bleach fix bath is deposited on the wall of the oxidationchamber 110 and on the cover plate 111 of the separator housing. Theremainder of liquid is removed from the air by entering the separator106 which forms a jacket surrounding the oxidation chamber 105, where itis deposited on the annular separator plates 113 which are attachedalternately to the external surface of the wall of the oxidation chamber110 and the internal surface of the wall of the housing 112. The airfreed from spray then enters the annular extension 114 at the level ofthe outlet connection 108 on the side diametrically opposite to the saidoutlet connection 108. This annular extension 114 surrounds theoxidation chamber 105 and on the side of the outlet connection 108 it iscontinuous with the semi-circular ring channel 115 which lies on theoutside of the wall of the housing 112. On that side, the wall of thehousing 112 does not have an annular extension in its width but ispartially continuous to form baflle 112 so that no bath liquid drippingfrom the separator plates 113 can be blown into the outlet connection108. The bath liquid deposited as described above is removed from theapparatus via the discharge pipe 107. Bath liquid which has beendeposited inside the oxidation chamber enters the discharge pipe 107through the aperture 116.

Another embodiment of an apparatus for carrying out the processaccording to the invention is illustrated in FIG. 2. The oxidationchamber 205 consists of a cylindrical tube 211 (wall of oxidationchamber) provided with a baseplate 209 and cover plate 210. The bathliquid supplied through the inlet 203 is atomized into the oxidationchamber 205 vertically from above through the onecomponent nozzle 201.In the plane of the outlet aperture of the spray nozzle 201 there is apartition 212 which a has an aperture 213 in the region of the spraynozzle 201. This aperture provides for automatic access of air from thechamber 214 formed between cover plate 210 and partition 212 into theoxidation chamber 205 when bath liquid is atomized into the oxidationchamber. The higher the rate of discharge of the bath from the spraynozzle 201, the more vigorously is the spray mixed with air. Chamber 214communicates with the outside air through a plurality of apertures 215.1 I I When the bath liquid has been sprayed into; the oxidation chamber,the spray is separated into-gaseous and liquid constituents bymeans ofthe separator 206 which in this case is arranged in the lower part ofthe apparatus. It is composed of several pipe elements 216 of differentdiameters which are boxed inside one another and which are attachedalternately to the baseplate- 209 and the circular plate 217. The airoutlet connection 208 is' ar'- ranged axially at the centre of thebaseplate. The air is sutficiently freed from moisture byrepeatedjdefiection so that it is free from spray when it leaves theoutlet connection 208. v

The deposited bath liquid collects on thejbaseplate 209 of the oxidationchamber205 and can be discharged through a discharge pipe 207. The inner"zones of the. separator 206 communicate with the discharge pipe 207through apertures 218. A knee bend trap 219 is connected to thedischarge pipe 207 to enable a sump to be formed and thereby prevent airfrom escaping through the dis-. charge pipe 207 or through the apertures218. The liquid collected at the bottom of the oxidation chamber 205 canbe completely discharged by opening the shut-off valve. 220 whenrequired, for example when work is finished. To prevent any siphonetfects in the knee bend trap 219, the upper horizontal portion of pipeand the adjacent vertical portion are made wider than the rest. v

FIG. 3 shows another apparatus for carrying out the process according tothe invention. The oxidation chamber 305 consists in this case of thecylindrical pipe 310 which is rigidly connected to the baseplate 309 andclosed at the top by the cover plate 311 so that there is no outlet atthe top. As in the case of FIG. 1, the atomized spray, from thetwo-component nozzle 302 is formed from the. bath liquid suppliedthrough the feed tube 303 and air supplied through the feed tube 304.The spray is reflectedfrom the cover plate 311 of the oxidation chamber305 and partly deposited as liquid. Subsequently, the ascending sprayfrom nozzle 302 and the return fiow of air together produce a vigorousturbulence which is very effective for the reoxidation process of thebleaching agent. Numerous apertures 312 are provided at the lower end ofthe wall of the oxidation chamber to enable air to escape. The lowerpart of the oxidation chamber 305 is surrounded by anannular jacket 313in the form of a vessel which is filled with bath liquid to the top ofthe overflow pipe 314 when the apparatus is in operation.

Inside the oxidation chamber 305, the excess pressure produced maintainsthe liquid level at'the height of the apertures 312. The spray mistformed in the oxidation chamber 305 then escapes to'the outside throughthe apertures 312 and on bubbling through the liquid which acts asseparator 306 in the annular jacket vessel 313 it is separated into itsconstituents so that only air free from spray can escape to the outside.The jacket 313 is widened'atthe top "to prevent spilling over the top byspraying or foaming. The

discharge pipe 307 with shut-off valve 315 serves to'ernpty'" theapparatus when operation is finished. When the apparatus is put intooperation after it has been emptiedQ-the process must be begun with asmall supply of air until sufiicient liquid has collected in the thedischarged spray.

FIG. 4 shows a flow diagram of the'recirculation air process. In thespraying device 401 including separator the spray mist is separated intoliquid 408 and gaseous jacket 313 to separate constituents 407 and 406.Part of the effiuent air 406 is to be reused and the remaining part 407is discharged out of the circuit. Oxygen or fresh air 404 is admixed tothe recirculated air 406 which is partly depleted of oxygen. The mixtureis pumped by the compressor 402 again into the spraying device, therebycarrying the bleaching or bleach-fixing bath to be reoxidized 405. Thelatter is supplied from the collecting vessel 403 wherein the liquid 408is collected. The bleaching or bleach-fixing process may be carried outwithin the spraying device 401 by spraying or alternatively by immersionin the bleach or bleach-fix bath collected in the collecting vessel.

FIG. 5 shows a longitudinal section through an apparatus in which thebleaching or bleach-fixing and the spraying are carried out in the samechamber. The chamber 501 is formed by the rectangular base plate 502,the side walls 503 and the cover plate 504. Within the chamher 501 aresituated several upper deflecting rollers 505 and lower deflectingrollers 506. A photographic web 507 with a silver halide emulsion layerto be bleached which is moved through the chamber at a constant speed isdeflected several times by the deflecting rollers thus forming severalsegment chambers 508 within the chamber 501. Several two componentnozzles 509 extend through the base plate and open into each of thesegment chambers 508. Oxygen or air is supplied by feed tube 510 and thebath to be reoxidized and applied to the silver halide emulsion layer ofthe photographic web 507 is supplied by feed tubes 511. The latter feedtubes are dipping to the bottom of a collecting vessel 512 whichcollects via the discharge pipes 513 the bath liquid deposited from thespray mist within the chamber 501. Underneath the lower deflectingrollers 506 the various segment chambers 508 are separated from eachother 'by partial dividing walls 514. The moist spraying gas from whichmost of the liquid has been separated within the chamber 501 is removedthrough the outlet connection 515 and can be conducted through aseparator for removing the remainder of liquid and/or can be refedwholly or partially into the chamber 501. If the front and rear walls ofthe apparatus (not seen in FIG. 5) have a distance that equals the widthof the photographic web, then each of the segment chambers 508 can beconsidered as a separate spraying and application chamber which islimited by the upper deflecting roller 505, the photographic web 507 thefront and rear wall (not seen), two partial dividing walls 514 and partof the base plate 502. In this case nearly no intermixture occursbetween difierent segment chambers 508 and it would be possible to havein different segment chambers photographic processing baths of differentcomposition.

FIG. 6 shows a longitudinal section through an apparatus according tothe invention which consists of an oxidation chamber 601 and a bubblingvessel 602 which is simultaneously used as processing tank. A twocomponent nozzle 603 extends through the bottom of the oxidation chamber601 and atomizes bleaching or bleach-fixing bath supplied by theprocessing tank (bubbling vessel) 602 through feed pipe 604. The gas forspraying (oxygen or air) is supplied by feed pipe 605. The spraying mistis partly separated into gaseous and liquid constituents and leaves theoxidation chamber 601 through the outlet pipe 606 which reaches to thebottom of the processing tank 602 where it has numerous apertures 607 toallow the gaseous constituents to bubble through the bath liquid in theprocessing tank. Several upper and lower deflecting rollers 608 providemeans for moving a photographic web 609 to be processed through thebleaching or bleach-fixing bath in the processing tank.

The process according to the invention will now be further explained bythe example which follows.

EXAMPLE An exposed color photographic multilayered material which'hadpreviously been treated with a developer was processed in a bleach-fixbath of the following composition:

Water up to 1000 ml. pH with acetic acid adjusted to 7.7.

Durin this treatment, the change in Redox potential of the bleach fixbath was continuously determined by means of a platinum electrodeagainst a silver-silver chloride electrode used as reference electrode.The Redox potential of the bleach fix bath was continuously deter-minedby means of a platinum electrode. The Redox potential was -25 mv. at thebeginning of the experiment and fell to 112 mv. in the course ofprocessing the photographic material, a reduction in bleaching activitybeing observed at the same time. The bleach-fix bath was then subjectedto electrolysis as generally carried out for desilvering photographicfixing baths. There was then practically no further change in Redoxpotential.

1st experiment Part of the desilvered bleach fix bath was sprayedthrough nozzle 102 in an apparatus according to FIG. 1 simultaneous witha supply of air. The residence time of the liquid in the apparatus wasof the order of several seconds. The bleach-fix bath collected from thedischarge tube had a Redox potential of 72 mv. after the first passingthrough the spray process. After a further passing through the sprayprocess, the Redox potential rose to 44 mv. and after a third sprayingit Was found to be 14 mv. When the bleaching capacity of thereconstituted bath was compared with that of a fresh bleach-fix bath thevalues were obtained substantially similar.

2d experiment The other part of the desilvered bleach fixed bath wasintroduced into a large tank which had a plastics tube provided withsmall apertures (diameter about 1 mm.) fitted into the base. Air wasthen injected into the bleach fixed bath through the plastics tube forminutes. The effect on the redox potential was only slight (increase to106 mv.) so that a method of injecting air by which comparatively largeair bubbles are formed must be regarded as practically useless.

3rd experiment The second experiment was modified in that the plasticstube was replaced by a glass frit G 4 with very small pores and air wasagain injected. Very fine bubbles of air were observed which permeatedthe bleach-fix bath almost homogeneously. At the same time, a bulky foamsettled on the surface of the bleach fix bath. After 60 minutes ofintensive admixture of air the redox potential, which rose in almostlinear progression, was 15 mv. When the bleaching capacity of the bathwas tested it was found to be comparable to that of a fresh bleach fixbath.

Experiments 1 and 3 show that spraying three times and injecting air for60 minutes through a glass frit produce practically the same results butthe undesirable formation of foam in the latter case renders reoxidationof the bleach fix bath in the processing tank impossible so thatadditional large storage tanks are required.

When comparing the residence times of the bleach fix bath in thereoxidation chamber (1st experiment) and in the tank (3rd experiment)the results of the spray process are found to be very favorable. Due tothe short processing time required for the reconstituted bleach fixbath, the

quantity of bath required in the cycle ofprocessingdesilvering-reoxidation is small so that it becomes possibleto use only small apparatus for a cycle including the working up of thebleach fix bath. Moreover,,wl1en changing the bath, the costs arisingfrom losses in the bleaching or bleach-fix bath are insignificant owingto the small volume involved.

In the apparatus described in the examples, liquid pumps or compressorscommonly known in the art are used for supplying the bleaching or bleachfix bath and air. The choice of devices used depends on the requiredrate of flow at the given delivery pressure. The choice of material isparticularly important in view of the corrosive nature of the baths. Forthe oxidation chamber and the tubes synthetic materials can be used suchas polyvinylchloride, polymethacraylate and polypropylene. The materialsused for the liquid pumps must also be highly corrosion-fast. Glass,porcelain or special metal alloys can be used for this purpose,preferably stainless steel such as 18 CrNi 8 (V 2 A, V 4 A) or HastelloyC, a trademark of Haynes Stellite Co. for a high-temp. nickel-base allocontaining 0.15% (max.) carbon, 13.0- 16.0% chromium,, 15.0-19.0%molybdenum, 3.5-5.5% tungsten, 4.0-7.0% iron, and the balance nickel. Inthe case of two-component nozzles (FIG. 1 and FIG. 3) the bath liquidmay be delivered to the spray nozzle at a lower pressure because theenergy required for atomization is derived almost completely from thecompressed air. The supply of air into the oxidation chamber may bepartly or completely separated geographically from the place whereatomization or the bath liquid takes place. Thus, for example aone-component nozzle for the bleaching or bleach fix bath and a nozzlefor supplying air may be arranged opposite each other so that vigorousturbulence is produced by the opposite directions of the jets of sprayand air, by which the reoxidation process of bleaching agent is greatlyassisted. Alternatively, a onecomponent nozzle or two-component nozzlemay be surrounded by a ring of air nozzles, by which a high rate of airflow in the same direction as the delivery of atomized bath liquid isprovided which is particularly suitable for dealing with large outputsof bath liquid in large apparatus.

This technique is highly advantageous because the air can be passedthrough the oxidation chamber at a high velocity, because the energynecessary for warming up the air to the temperature of the sprayingprocess can be kept low, and because the oxygen content can becontrolled exactly and easily. During the process oxygen is used up andhas to be replaced. If pure oxygen is supplied in the recirculating airprocess, it is even possible to have the circuit closed, so that nooutgoing air is taken off. In this case in FIG. 4 the outlet connectionis closed. The oxygen which ma be fed in from an oxygen cylinder is usedcompletely and on the other hand the mist formed by spraying has not tobe separated thoroughly into gaseous and liquid phases. Since thetechnique of recirculating air process is quite generally known (e.g.for drying processes; reference is made for example to A. G. Kassatkin,Chemische Verfahrenstechnik, volume II,. VEB Deutscher Verlag fiirGrundstofiindustrie, 5th edition, Leipzig 1962) it requires no furtherexplanation here. Since oxygen is used up in the reoxidation ofbleaching agent, the air after it has passed through a separator. may befed into a reaction chamber for photographic processing stages which aresensitive to oxidation, e.g. development by a spray process, hobberapplication process or roller application process. It is particularlywhen an air recirculation process with admixture of fresh air isemployed that the air partly depleted of oxygen may assume the functionof a protective gas, e.g. if the recirculated air is introduced into theappropriate reaction chamber before it is mixed with fresh air.

The process is advantageously carried out at elevated temperatures (upto 50 C.) in order to accelerate the reoxidation process. In that case,if the oxidation chamber is connected to a processing machine, thetemperature may be regulated by the temperature control unit of thebleaching or bleach fix bath. It is especially advantageous if theoxidation chamber in which reoxidation of the bleaching agent takesplace serves at the same time as the processing chamber for bleaching orbleach fixing because the integration of reconstitution of the bleachingagent with processing enables small machines to be used.

In one special embodiment, the wall of the oxidation chamber is partlyformed by the silver halide emulsion layers of a photographic materialwhich is moved at constant speed. The oxidation chamber may, forexample, have a rectangular cross-section, two fixed side walls facingeach other being formed by the apparatus while a band of photographicmaterial passing through the apparatus is deflected through by adeflecting roller so that it forms the other two side walls of theoxidation chamber.

Lastly, the air which has passed through the oxidation chamber may beconducted through a bubbling vessel which functions as a separator andwhich at the same time constitutes the processing tank or part of theprocessing tank for the bleaching or bleach fixing process. Thisarrangement not only ensures efficient separation of the atomized spraybut also provides for thorough agitation of the processing bath so thatthe time required for bleaching may be expected to be reduced.

We claim:

1. A process for the continuous reoxidation of used photographicbleaching and bleach fix baths, characterized in that the used bleachfix bath is atomized and injected into contact with gaseous oxygenwhereby the used bleach fix bath is reoxidized essentially to itsoriginal chemical state, and the atomized spray containing the oxidizedbleach fix bath is caused to directly impinge upon a separation mediumfor separating out and recovering the liquid constituents.

2. A process according to claim 1, characterized in that the bleach fixbaths are atomized in the presence of air.

3. A process according to claim 1 wherein the gaseous oxygen in contactwith which the bleach fix baths are atomized is provided by recycled airand wherein the oxygen depleted in the reoxidation is replaced by theaddition of fresh air or oxygen.

4. A process according to claim 1 wherein the bleach fix baths areobtained from photographic bleaching or bleach fixing processes whichare performed at a range of processing temperatures, and wherein thereoxidation is performed at about the same processing temperature range.

5. A process according to claim 4 wherein the processing temperaturerange is up to about 50 C.

6. A process according to claim 1 wherein the bleach fix baths areobtained from photographic bleaching or bleach-fixing processes whichare performed in a chamber, and the reoxidation is performed in the samechamber.

7. A process as set forth in claim 6 wherein the bleaching or bleachfixing is performed by atomizing the bleach fix baths and thereoxidation is performed by the atomization which occurs in thebleaching or bleach fixing.

8. A process according to claim 1, characterized in that the gaseouscomponents which are depleted in oxygen and separated from liquidconstituents are used as protective gas for other photographic stepswhich are sensitive to oxygen. 1

9. A process according to claim 1 wherein the reoxidation is performedin an oxidation chamber, the gaseous constituents being removed from thechamber, and the gaseous constituents being separated from the liquidconstituents by bubbling them through a liquid.

10. A process according to claim 8 wherein the liquid through which thegaseous constituents are bubbled is utilized in the bleaching or bleachfixing process.

(References on following page) References Cied UNITED OTHER REFERENCESSTATES PATENTS Pifer 96.63 RONALD H. SMITH, Primary Examiner Cooley 9-60 F KELLEY A Schurig g a] a 261-77 5 sslstant Exammer Laird 261-Di'g.75 US. Cl. X.R-. Matasa et a1. 261---Dig. 7S 95-50 0 2 5 R, 284

Kodak Research Disclosure, October 1972, pp. 17-19.

